6-alkyl-alpha-pyrones are valuable substances useful in the formulation of perfumery, tobacco and food flavoring materials, as disclosed in copending application for U.S. Letters Pat. No. 471,755 filed on May 20, 1974 and copending application for U.S. Letters Pat. No. 471,785 filed on May 20, 1974. Nobuhara, Agr. Biol. Chem. 1969; 33, No. 9, 1264-9 (Title: "Synthesis of Unsaturated Lactones/III, Flavorous Nature of Some .delta.-Lactones having the Double Bond at Various Sites") indicates the waxy, buttercake flavor of 6-pentyl-alpha-pyrone (pg. 1267, col. 1). In addition, the flavor attributes of 6-alkyl-alpha-pyrones, in general, are discussed. Sevenants, J. Food Sci. 1971, 36 (3) 536 discloses the occurrence of 6-pentyl-alpha-pyrone in peach aroma.
The preparation of 6-alkyl-alpha-pyrones is set forth in several references, to wit: a. Lohaus, Chemische Berichte, 100, 658 (1967) discloses a reaction as follows: ##EQU2## wherein R.sup.1, R.sup.3 and R.sup.5 are the same or different alkyl and R.sup.2 and R.sup.4 are hydrogen or alkyl.
As is indicated in Example I, infra, the yield of 6-alkyl-alpha-pyrones without other ring substituents obtained in carrying out the Lohaus et al. reaction sequence is so low as to cause this process to be commercially impractical.
The Nobuhara paper, cited supra, discloses a multi-step synthesis which gives rise to less than a 10% yield of 6-alkyl-alpha-pyrone, thusly: ##SPC4##
The multi-step sequence of reactions and the low yield of final product render the Nobuhara synthesis commercially impractical.